1. Field of the Invention
The present invention relates to a handheld electromotive tool with a sensor, especially to an electric driven screwdriver having a level sensor.
2. Description of the Related Art
Screwdrivers containing electric motors are generally used in construction fields, and they contribute to improvement of the efficiency in work such as fastening bolts. On the other hand, a method of construction has attracted attention in which ceiling boards and/or floor boards of construction such as buildings and houses are set up so that their levels (heights) can be adjusted if necessary and wirings of electronics and various kinds of apparatus can be installed in the ceiling and or under the floor.
A typical example of a floor board set up according to said method of construction will be described with reference to FIG. 13. Many bearing bolts 2 are revolvably held over the surface of a foundation slab 1, wherein the bearing bolts are arranged substantially perpendicularly. Many nuts 4 which are engaged with corresponding bearing bolts 2 are embedded in a floor board 3. The floor board 3 can be vertically shifted according to the pitch of the screen threads by rotating the bearing bolts 2 one by one with an electric driven driver 5. Similarly, a ceiling board set up according to said method of construction can be vertically shifted by rotating bearing bolts embeddedly provided in a ceiling foundation slab one by one.
In order to set up the floor board 3 horizontally, the amounts of engagement of all the nuts 4 with respective bearing bolts 2 have to be the same and constant. Of course, it is possible to horizontalize the floor board 3 by using a spirit level. But it is highly inefficient to horizontalize the floor board 3 everytime each of many bearing bolts is rotated by the electric driven screwdriver. Also, such work requires skill.
In order to avoid said inconvenience, in Japanese Utility Model Application Laid-open No. 3-120374, technique for controlling rotation of an electric driven screwdriver according to output of a photo detector has been proposed, in which a photo detector for receiving a laser beam rotating in a reference flat plane is mounted on an electric driven screwdriver. According to this prior art, as the electric driven screwdriver is stopped when the laser beam is received as a reference position of the photo detector, the amounts of engagement of all the nuts 4 with respective bearing bolts 2 can be made to be the same and constant. However, as the motor will not stop as soon as the laser beam reaches said reference position, the floor board can be set exactly at the target position only after repeating normal and reverse rotations of the motor several times.